Instant regeneration.
Superior sensing
Sage Mode
Mokuton clones that only 1 person can tell apart.
None of Tobirama's ninjutsu is fast enough to catch Minato. He outspeeds the 8th Gate in terms of reaction time, so his small scale suiton ninjutsu or Edo Tensei paper bomb ninjutsu really doesn't matter here. It'll be these two slashing each other to death.